This invention relates to shaving razor blades and stock material, manufacturing methods and apparatus therefor.
Razor blades are typically made from a continuous strip of stock material that is hardened and sharpened while the strip travels along a processing line. The strip is then divided in blade length sections used in manufacture of individual cartridges.
In some applications, blades are supported on bent supports that are slidably mounted in the cartridge housing to move up and down during shaving. E.g., FIG. 1 shows cartridge 10 with blades 12 slidably mounted in housing 14, and FIG. 2 shows a blade 12 on a support 16. In these applications, the blades cannot overlap and thus have a small dimension xe2x80x9caxe2x80x9d from the cutting edge to the back edge 20. The strip material and blade sections, however, must have a sufficient distance from the front edge to the back edge in order to properly secure and hold the material and sections during processing and attaching to blade supports. It thus is necessary to remove a portion of the blade material after processing and attaching so that the blade will have the desired small dimension from the cutting edge to the back edge. In some applications, the rear section 22, shown in FIG. 3, is removed by bending the rear section 22 between 60xc2x0 and 90xc2x0 with respect to the front section 24 after the front section has been attached to the blade support. FIG. 3 also shows spot weld 26, used to attach blade 12 to support 16. There typically is an upturned portion at the rear edge 20 of the attached blade section where the rear section has been removed. In some cases the rear section 22 is not easily removed.
In one aspect, the invention features, in general, an elongated stock material for use in manufacturing shaving razor blades. The stock material is made of an elongated, flat strip of metal having a front edge and back edge extending along its length. The material has a sharpened cutting edge portion extending along the front edge, a weakened portion between the front edge and the back edge, a blade portion between the cutting edge portion and the weakened portion, and a removable portion between said weakened portion and back edge.
In preferred embodiments, the weakened portion has a reduced thickness compared to the blade portion and the removable portion. The weakened portion has a first notch portion on one side, and a second notch portion on the other side. The notch portions are offset with respect to each other. Each notch portion has a steep surface and a gradually deflecting surface. The weakened portion is located between xc2xc and xc2xe of the distance from the front edge to the back edge.
In another aspect the invention features, in general, a shaving razor blade including a metal blade having a front cutting edge portion and a back edge, the back edge having a weakened portion from which a removable portion has been removed by bending at the weakened portion.
In preferred embodiments, the blade is mounted on a support member attached to the metal blade. The support member has a base portion that generally extends along a plane that makes an angle between 90 degrees and 135 degrees with a plane extending through the blade. The back edge has a slight bend that is straighter than it would be if the separable portion did not have the weakened portion and has a radius instead of an upturned edge.
In another aspect, the invention features, in general, a shaving razor cartridge including a housing, and one or more blades attached to the housing. Each blade having a front edge having a cutting edge portion and a back edge, the back edge having a weakened portion from which a removable portion has been removed by separating at the weakened portion.
In another aspect, the invention features, in general, a method of making razor blades by providing an elongated, flat strip of metal having a front edge and back edge extending along its length, sharpening the front edge to result in a cutting edge portion extending along the front edge, and weakening a portion of the strip along its length between the front edge and the back edge to result in a weakened portion extending along the strip, a blade portion between the cutting edge portion and the weakened portion, and a removable portion between the weakened portion and the back edge.
In preferred embodiments, the weakening includes forming a crease to provide the weakened portion. The weakening includes deforming a portion of the strip to reduce its thickness to provide the weakened portion. The weakening includes a notch formed on one or both sides of the strip. The strip is deformed by passing the elongated flat strip between two rollers. The deforming includes passing the elongated flat strip between two rollers having different profiles and spaced sufficiently close to each other to cause the portion of the strip to be deformed when passing between them. The strip is cut into discrete blade sections. The blade portions of respective blade sections are attached to respective blade support members. The removable portions are separated from the blade portions by bending at the weakened portions.
In another aspect, the invention features, in general, apparatus for making razor blade material that includes a continuous supply of an elongated, flat strip of metal having a front edge and back edge extending along its length, a processing line along which the flat strip from the supply moves, a sharpening station on the processing line through which the strip passes and at which the front edge is sharpened to result in a cutting edge portion extending along the front edge, and a processing station on the processing line through which the strip passes and at which a portion of the strip between the front edge and the back edge is weakened to result in a weakened portion extending along the strip, a blade portion between the cutting edge portion and the weakened portion, and a removable portion between the weakened portion and the back edge.
In preferred embodiments, the processing station includes two rollers through which the strip passes. The two rollers have different profiles and are spaced sufficiently close to each other to cause the portion of the strip to be deformed when passing between them. Each roller has a large diameter portion and a small diameter portion, the large diameter portion of one the roller being generally aligned with the small diameter portion of the other the roller. Each roller has a thin portion between the small diameter portion and the large diameter portion, the thin portion having a diameter that is less than the diameter of the small diameter portion.
Embodiments of the invention may include one or more of the following advantages. Use of a weakened portion permits one to have a large width to facilitate blade sharpening and attaching to a support, yet also permits a small distance from the cutting edge to the rear edge in the final shaving razor blade product. The use of a weakened portion also permits one to use a softer and higher corrosion resistant material that otherwise would be difficult to separate by bending. The weakened portion permits one to use different types of blade steel and steel provided from various suppliers that normally will not fracture without such weakening. This can permit use of a smaller stock thickness (e.g., 0.002xe2x80x3 instead of 0.003xe2x80x3, as presently used), which generally is more difficult to fracture. (I.e., thinner stock would be more likely to bend than fracture).
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.